Actuating device employing a heat expansible wire

ABSTRACT

The present actuator employs a heat expansible element and is of the type actuator known as a &#39;&#39;&#39;&#39;hot-wire&#39;&#39;&#39;&#39; actuator. The present actuator has an extremely simplified structure formed by two substantially J-shaped frame members, the arms of which are interconnected by insulating members; a thermally expansible element extending between the base portions of the frame members, which base portions also have depending legs serving both as terminals and supports for the frame; and linkage means responsive to the tension of the element as it expands and contracts to produce movement useful for actuating switches, valves, etc.

United States Patent Tyler 51 Sept. 12, 1972 [54] ACTUATING DEVICEEMPLOYING A HEAT EXPANSIBLE WIRE [72] Inventor: Hugh J. Tyler, SantaAna, Calif.

[52] US. Cl. ..337/l23, 60/23, 337/398 [51] Int. Cl. ..H0lh7l/l8 [58]Field of Search ..337/123, 126, 139, 140, 395,

Primary Examiner-Bernard A. Gilheany Assistant Examiner-F. E. BellAttorney-Anthony A. OBrien et a1.

[5 7] ABSTRACT The present actuator employs a heat expansible ele mentand is of the type actuator known as a hotwire actuator. The presentactuator has an extremely simplified structure formed by twosubstantially J- shaped frame members, the arms of which areinterconnected by insulating members; a thermally expansible elementextending between the base portions of the frame members, which baseportions also have depending legs serving both as terminals and supports[56] References Cited for the frame; and linkage means responsive to theUNITED STATES PATENTS tension of the element as it expands and contractsto produce movement useful for actuating switches, 3,169,180 2/1965Chafer ..337/l40 X valves em 3,254,178 5/1966 Voorman ..337/140 X3,254,180 5/ 1966 Flanagan ..337/ 140 X 3 Claims, 4 Drawing Figures l44- I 5s 9 h I l '1 m 0 .1 I I 47 I r U 45 PATENTEnszrlzmz 3,691,499

FIG. 29

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42 4 e 52 If 49 L 11L HIV :1: FIG. k 58 "Pl I iflgfl m R4111! M" 45ACTUATING DEVICE EMPLOYING A HEAT EXPANSIBLE WIRE BACKGROUND OF THEINVENTION 1. Field of the Invention The present invention relates toactuators of the general type known as hot-wire actuators in which, whenenergized, a thermally expansible element heats and expands, themovement of expansion being transmitted to a device to be actuated.

2. Description of the Prior Art An example of the known hot-wireactuators has been shown in FIGS. 1 and 2. These known actuators haveprovided the desired actuator operation through the movement of athermally expansible element but generally suffer from the disadvantageof having a large number of parts and are both difficult and expensiveto assemble and adjust for a desired accuracy.

1 SUMMARY OF THE INVENTION It is, therefore, an object of the presentinvention to provide an improved actuator consisting of a few simpleparts which are both low in cost and easy to assemble.

It is a further object of this invention to provide a means forassembling the improved actuator by using loose fitting,easy-to-assemble insulators and frame members in such relationship withone another that their looseness or play will not affect the precisionof the thermal operator output.

The inventive thermally responsive actuator is formed by a frame havingtwo identical .I-shaped frame elements with insulating membersconnecting the long leg of each element with the short leg of the otherelement. Base portions of the frame elements have terminals extending atright angles to the plane formed by the legs and serving both aselectrical connectors and to mount the frame in a casing. A strip-shapedelement of thermally expansive material is connected between baseportions of the frame elements and linkage means are operativelyconnected between the thermally expansive element and the device to beactuated so that the movements of the former will be transmitted to thelatter.

These and other objects and advantages of the present invention willbecome apparent from the following detailed description of a preferredembodiment viewed in conjunction with the accompanying drawings, inwhich:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a longitudinal verticalsection of a known hot-wire actuator;

FIG. 2 is a top plan view of the actuator of FIG. 1;

FIG. 3 is a longitudinal vertical section of the improved actuator ofthe present invention; and

FIG. 4 is a top plan view of the inventive actuator of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT The known actuator shown inFIGS. 1 and 2 has a casing with terminals 11 and 12 fixed on theexterior thereof. A generally C-shaped frame 13 is mounted within andspaced on all sides from the casing 10 by brackets 14 and 15 and screws16 and 17. The frame is insulated from the casing by insulators 18 to23. Lead 24 passes through an aperture 25 in the casing to electricallyconnect terminal 11 to closed end 26 of the frame 13. A strip ofthermally expansible material 27, known as a hot-wire, is fastenedbetween the closed end 26 and an insulating roller 28, which isrotatably mounted by axle 29 across the open end 30 of the frame 13. Asecond lead 31 electrically connects the terminal 12 to the strip 27through orifice 32. A link 33 is fastened by one end to an intermediateportion of the strip 27 and extends through aperture 34 in casing 10with its other end operatively connected to lever 35. Lever 35 has oneend pivotally attached to the casing at 36 and has its other end biasedfor clockwise rotation by helical compression spring 37.

This known actuator is operated by energizing the electrical circuitincluding terminal 11, lead 24, frame 13, strip 27, lead 32 and terminal12 to heat the thermally expansible strip 27. As the strip 27 heats andexpands, it will be drawn downward by the action of the bias spring 37through lever 35 and link33, thereby producing a clockwise movement ofthe free end of the lever 35, which movement can be transmitted in aknown manner (not shown) to the device being actuated. When the circuitis deenergized, the strip will cool and contract thus causing acounterclockwise movement of the lever 35 against the force of spring37.

The present invention, shown in FIGS. 3 and 4, has a casing 38 withterminals 39 and 40 fixed on the exterior thereof. The frame 41 of theinventive actuator is formed by two identical frame elements 42 and 43.Each frame element has a generally .I-shaped profile formed by baseportions 44 and 45, long arms 46 and 47, and short arms 48 and 49 withterminal legs 50 and 51 depending from the base portions normal to theplane defined by the J-shaped profile. The frame is assembled byconnecting arms 46 and 49 in fixed spaced relation by means of insulatorelement 52. Arms 47 and 48 are similarly connected by insulator element53. The terminal legs 50 and 51 are, respectively, passed throughapertures 54 and 55 and connected to terminals 39 and 40 by screws 56and 57. Legs 50 and 51 thus serve to both fix the frame within andspaced on all sides from the casing and as electrical connectionsbetween the terminals and the strip of thermally expansible material 58,which is fixed between the base portions 44 and 45. Link 59 has one endattached to the strip and its other end passing through aperture 60where it is attached to lever 61. Lever 61 has one end pivoted to casing38 at pivot 62 and the other end biased for clockwise rotation byhelical compression spring 63.

When the circuit including terminal 39, leg 50, base portion 44, strip58, base portion 45, leg 51, and terminal 40 is energized, the strip 58will heat, expand, and be drawn downward by link 59, lever 61 and spring63. Insulator elements 52 and 53 insulate and mechanically restrain theframe arms as the thermally expansible strip expands and is drawndownwards so that the movement of the lever will reflect substantiallyonly the expansion of strip 58.

A feature of the present invention is the loose fit of the insulatorelements on the frame arms which acts to restrain any appreciablemovement of the strip supporting base portions towards one another. Theyalso serve to prevent any twisting motion of the frame assembly duringmovement of the hot-wire in order to achieve the desired, and farsuperior, mechanical stability of the frame.

The low manufacturing cost of the parts and the assembly can beappreciated by visualizing the individual parts. identical long andshort frame arms are inserted into identical insulator elements. Ahot-wire is spotwelded to the base areas of the frames to complete theself-supporting thermal actuator which can be assembled as a unit to themechanism to be operated.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. Therefor theforegoing description is intended in all respects as illustrative andnot in a limiting sense.

What is claimed is:

l. A thermal responsive actuator comprising a casing,

a frame comprising two substantially identical frame elements mounted insaid casing,

each said frame element having a generally J-shaped configuration formedby a long arm and a short arm extending from a base portion and aterminal portion extending from said base portion normal to the plane ofsaid arms, insulating means connecting said arm portions of one of saidframe elements to said arm portions of the other of said elements,thermally expansive wire means connected between said base portions ofsaid frame elements, and means connected to said wire means to beresponsive to the movement thereof and to effect a useful movement. 2. Athermal responsive actuator according to claim 1 wherein said meansconnected to said wire means comprises,

lever means having one end pivotally mounted on the exterior of saidcasing, spring means biasing the other end of said lever means away fromsaid casing, and link means passing through said casing with one endattached to said wire means and the other end attached to said levermeans. 3. A thermal responsive actuator according to claim 1 whereinsaid frame is mounted with said terminal portions projecting out of saidcasing thereby forming electrical connection terminals for the actuator.

1. A thermal responsive actuator comprising a casing, a frame comprisingtwo substantially identical frame elements mounted in said casing, eachsaid frame element having a generally J-shaped configuration formed by along arm and a short arm extending from a base portion and a terminalportion extending from said base portion normal to the plane of saidarms, insulating means connecting said arm portions of one of said frameelements to said arm portions of the other of said elements, thermallyexpansive wire means connected between said base portions of said frameelements, and means connected to said wire means to be responsive to themovement thereof and to effect a useful movement.
 2. A thermalresponsive actuator according to claim 1 wherein said means connected tosaid wire means comprises, lever means having one end pivotally mountedon the exterior of said casing, spring means biasing the other end ofsaid lever means away from said casing, and link means passing throughsaid casing with one end attached to said wire means and the other endattached to said lever means.
 3. A thermal responsive actuator accordingto claim 1 wherein said frame is mounted with said terminal portionsprojecting out of said casing thereby forming electrical connectionterminals for the actuator.